1. Technical Field
The present relates to an electrostatic latent image developing toner (hereafter also referred to as an electrophotographic toner), an electrostatic latent image developer, an image forming apparatus, and an apparatus for manufacturing an electrostatic latent image developing toner.
2. Related Art
Methods of visualizing image information by using an electrostatic latent image, such as electrophotographic methods, are currently used in a wide variety of fields. In an electrophotographic method, an electrostatic image is formed on a photoreceptor by charging and exposure, this electrostatic image is developed with a developer that includes a toner, and the toner image is then transferred and fixed to complete visualization of the image. Developers that can be used in this type of electrophotographic method include two-component developers that are formed from a combination of a toner and a carrier, and one-component developers in which a magnetic toner or non-magnetic toner is used alone. The method of manufacturing the toner usually employs a kneading-grinding method in which a thermoplastic resin is subjected to melt kneading with a pigment, a charge control agent and a release agent such as a wax, and the resulting mixture is subsequently cooled, grinded finely, and then classified. If required, inorganic or organic particles may then be added to the toner and adhered to the surface of the toner particles in order to improve the toner fluidity and cleaning properties.
In a typical kneading-grinding method, although only minor variations occur in the grindability of the materials used and the conditions during the grinding step, the toner shape and the toner surface structure are irregular, and systematic control of the toner shape and surface structure is difficult. Furthermore, particularly in the case of toners that employ materials with a high degree of grindability, the toner particles are often ground further by mechanical forces within the developing unit, thereby inviting the generation of a very fine powder and causing variation in the shape of the toner. As a result of these effects, charge degradation of the developer caused by the fine powder affixing to the surface of the carrier tends to occur in two-component developers, whereas in one-component developers, the broadening of the particle size distribution tends to cause toner scatter, and the variation in toner shape tends to cause a deterioration in the developability that increases the possibility of image degradation.
On the other hand, in recent years there has been a shift to the use of toners manufactured using polymerized methods. In a polymerized method, a spherical toner is usually obtainable. One feature of spherical toners is that they offer a high degree of transferability. However, in a suspension polymerization method, the preparation of irregularly shaped toner particles is problematic, and the average sphericity is usually 0.98 or higher. Although spherical toner with a sphericity of 0.98 or higher exhibits a high degree of transferability, when residual non-transferred toner left on the photoreceptor needs to be removed by cleaning, satisfactory cleaning may not be achievable using a normal blade cleaning technique.